Various electric appliances are coming into wide use and a wide variety of appliances are on the market. In particular, in recent years the spread of portable electronic devices has been marked. As an example, portable telephones, digital video cameras, and the like, have become very convenient, having display portions with high definition and batteries that are more durable and have low power consumption. As a power source for driving portable electronic devices, a battery, which is a charging means, is built-in. As a battery, a secondary cell (hereinafter referred to as a ‘battery’) such as a lithium ion battery is used. As matters now stand, the battery is charged from an AC adaptor which is plugged into a household alternating current power supply, which is a power supply means (see Reference 1: Japanese Published Patent Application No. 2005-150022).
Note that means of transportation such as bicycles, motor vehicles (including electric vehicles, and means of transportation that drive forward by electric power, regardless of whether they have four wheels or two), and the like are also included in the category of electronic devices having a battery. Accordingly, in this specification, portable electronic devices and means of transportation which have a battery are all referred to as ‘movable electronic devices’ (‘movable devices’).